Digital data in the form of binary information has long been carried on optical fibers. Nowadays, the network of optical fibers spans the globe, forming the backbone of the Internet, the intranet, and extending all the way to the curb or even inside residences and businesses.
In the past, each optical fiber carries information unidirectionally (in only one direction such as in the transmit direction or in the receive direction), and a pair of optical fibers would be employed to implement a bidirectional flow of information between two communicating devices.
Bidirectional fibers carry data in both directions. Since each fiber carries both the transmit data and the receive data, the bandwidth capacity of each fiber is essentially doubled. Generally speaking, different wavelengths are employed for the two directions of information flow on each fiber. Multi-mode optical fiber technology has been employed to good effect to enable bidirectional traffic on optical fibers, for example.
Data monitoring using network taps has also been widely implemented. In network tapping, a portion of the information flow or the entire information flow on the fiber may be tapped, or duplicated, to be sent to a monitoring device. When data flow is only unidirectional on each fiber, tapping has been relatively straightforward. In an example, a splitter may be employed to receive data from the optical fiber (which data is sent from some transmitting equipment) and to provide two outputs. The first output provides the same data stream onward to the receiving equipment. The second output provides some or all of the same data stream to the monitoring equipment.
In this manner, the data is still transmitted from the transmitting equipment to the receiving equipment if desired. However, some or all of the data is duplicated and provided to the monitoring equipment. The tapped or duplicated data permits the monitoring equipment to perform tasks such as malware detection, network monitoring, access control, and the like. Optical network taps are available from vendors such as Ixia Corporation of Calabasas, Calif. and will not be further elaborated here.
Bidirectional traffic on each fiber, while increasing the bandwidth capacity of the fiber, complicates tapping. Tapping is particularly challenging when data is transmitted and received at high speeds, such as at 10 gigabits/second or above.
Embodiments of the subject matter described herein relate to methods and apparatus for efficiently tapping data on optical fibers that carry high speed bidirectional data traffic.